Game of Thrones' Kit Harington: "Oh God, I'm a Bastard!"

It's also a challenge playing one. Newcomer Kit Harington tells TVGuide that he had to learn to embrace the term "bastard," which is used quite frequently and openly in the series to describe his character Jon Snow, the illegitimate son of Winterfell's Lord Ned Stark (Sean Bean).

"When I first read that, I was like, 'Oh God, I'm a bastard!'" Harington confesses. "That's a weird thing to be called throughout the series. I hope people don't find that part of it funny. I have to find it serious for Jon ultimately, and so this word — which we use in England all the time as kind of an offensive thing — became something different. That's part of who he is. ... He should own it and use it to make him stronger. So something he was fighting against becomes something he is and is proud of."

In "Lord Snow," the third episode of Game of Thrones airing Sunday at 9/8c on HBO, Jon Snow, accompanied by his direwolf, Ghost, has left behind his legitimate half siblings at Winterfell to go live at Castle Black. There, he'll begin to shape his destiny as one of the black-clad Night's Watch at The Wall. "In this world, if you're an illegitimate child, it's almost tantamount to being a criminal," Harington says. It's appropriate then, that Jon is joining the criminals, superfluous third sons and other unwanted in society who populate the Night's Watch to defend the Seven Kingdoms from a threat north of The Wall.

It's not an easy life. Being part of the Night's Watch requires you to relinquish any previous alliances (i.e. your family), become celibate and accept the fellow watchmen as your new brothers. In short, once you wear the black, your blood runs black.

"This is the only place he can go to to fulfill his own ambition and be his own man like his Uncle Benjen is," Harington says. "When he gets there, he's surrounded by very unsavory types and it's not what he expected. It's not this glorious mission he thought he'd be going on. He finds it very difficult. I don't think he realized quite what letting go of his family and completely giving his loyalty to the Night's Watch means. He thought it would alleviate all these problems he had at home, but it doesn't do that. It adds more."

Oddly enough, it's the dwarf Tyrion Lannister (Peter Dinklage) who helps with Jon's transition, although they have a reluctant friendship at first. "Jon knows the Lannisters are kind of archenemies with his father and he's very loyal to his father, so immediately he's on the backfoot with Tyrion," Harington says. "He doesn't like him, but he sees straightaway that this is another person who's an outsider like he is. Jon sees him as someone who's taught him how to own himself and work with the other boys at Castle Black. I think they have a really interesting dynamic between them."

The scenes at Castle Black also posed more physical challenges for Harington. Besides enduring shooting in "truly hideous" freezing weather some nights in Belfast, he also had to brush up on his swordsmanship. In Episode 3, Game of Thrones fans finally get to see a character really wield a sword when the boys drill. As a lord's son (albeit an illegitimate one), Jon is one of the only Watch trainees who already has skills with a blade.

"He's trained all his life to be a great swordfighter so he can be fight alongside his father and be this hero," Harington explains. "So I wanted to make sure I looked I knew what I was doing. I had some training in drama school with swords, but it had been a while. So I started seeing a personal trainer three times a week just to get into a place where I was strong enough to wield the sword in a way that looked like I had been doing it for years and years and years.

"We had a great stunt coordinator and fight trainer called Buster who put us through our paces," he continues. "So the day before we went through some of the fights and the next day we were on set filming. In between takes we were just going through them again and again and again. They were put together so well that hopefully they'll look good."

There was one aspect of playing Jon, however, that no amount of training could help Harrington control: Acting opposite a dog named Cooper, which plays Jon's direwolf.

"Working with animals is always going to be tough because the animal doesn't know it's an actor," Harington explains. "It doesn't know what the hell's going on. It just wants the bit of meat you've got in your hand. Cooper may only get it right once, so you've got to make sure that your take's perfect every time because the one they're going to take is the one where the dog's got it right."

Game of Thrones airs Sundays at 9/8c on HBO. Check out this clip of Jon fighting at Castle Black in Sunday's episode: